Reported is the inverting and non-inverting operation of indium phosphide (InP)-based microdisc modulators heterogeneously integrated on a silicon-on-insulator waveguide. The light transmitted through the waveguide can be modulated in an inverting and non-inverting manner depending on the bias conditions. Static extinction ratios and dynamic operation of the device up to 2.5 Gbit/s are demonstrated. Clean open eyes with extinction ratios better than 6 dB are shown and operation with a bit error rate below 1×10−10 is demonstrated at 1.0 Gbit/s for both operation modes with a bias of only 1 Vpp.